Mobile communication devices may include one or more Subscriber Identity Module (SIM) cards that provide users with access to multiple separate mobile telephony networks. A mobile communication device that includes one or more SIMs and connects to two or more separate mobile telephony networks using one or more shared radio frequency (RF) resources/radios may be termed a “multi-standby” communication device. An example is a dual-SIM-dual-standby (DSDS) communication device, which includes two SIM cards/subscriptions that are each associated with a separate radio access technology (RAT), and the separate RATs share one RF chain to communicate with two separate mobile telephony networks on behalf of their respective subscriptions. Another example is a single-radio LTE (SRLTE) communication device, which includes one SIM card/subscription associated with two RATs that share a single shared RF resource to connect to two separate mobile networks on behalf of the one or more subscriptions.
A plurality of RATs on a multi-standby communication device may use one or more shared RF resources to communicate with their respective mobile telephony networks, and only one RAT may use each RF resource to communicate with its mobile network at a time. Even when a RAT is in an “idle-standby” mode, meaning it is not actively communicating with the network, it may still need to periodically receive access to a shared RF resource in order to perform various network operations. For example, an idle RAT may need the shared RF resource at regular intervals to perform idle mode operations, to receive network-paging messages in order to remain connected to the network, etc. on behalf of its subscription. Therefore, it is possible that at a certain times the multiple RATs sharing an RF resource may need to use the RF resource to communicate with their respective mobile networks simultaneously.
In conventional multi-standby communication devices, the RAT actively using an RF resource that is shared with an idle RAT may occasionally be forced to interrupt its RF operations so that the idle RAT may use the shared RF resource to perform its idle-standby mode operations (e.g., paging monitoring, cell reselection, system information monitoring). This process of switching access of the shared RF resource from the active RAT to the idle RAT is sometimes referred to as a “tune-away” or a “tune-away event,” as the RF resource must tune away from the frequency bands and/or channels of the active RAT and must tune to frequency bands/channels of the idle RAT. After network communications via the idle RAT (sometimes collectively referred to herein as “tune-away” operations) are complete, the communication device may switch RF resource access back from the idle RAT to the active RAT.
As a result of the tune-away event, data received using the active RAT may be lost or corrupted and thus may be difficult or impossible to decode. Tune-away events thus present a design and operational challenge for multi-standby communication devices and other shared-radio devices.